Hemisynthesis, NMR Characterization and UHPLC-Q-Orbitrap /MS² identification of (+)-Catechin oxidation products in red wines and grape seed extracts

The viticultural regions of the world have the advantage of a remarkable diversity of landscapes which are the reflection of the winegrowers’ capacity to adapt to the different geomorphological and climatic specificities of the terroirs, more generally speaking, this aesthetic and heritage aspect of the terroir is also part and parcel of the notion of sustainable viticulture.

The disruptive effect exerted by high-power ultrasound (US) on plant cell walls, natural barriers to the diffusion of compounds of interest during the maceration of red wines, is established as the reason behind the chromatic improvement that its treatment causes. However, sometimes this improvement is not observed, especially with short maceration times. The presence of a high quantity of suspended cell wall material, which formation is favored by the sonication, could be the cause of this lack of positive results since this cell wall material has a high affinity for phenolic compounds.

La superficie actuelle de l’ensemble des vignobles est de 5.293 ha qui est repartie dans 27 communes (données officielles du Conseil National des Communes de montagnes).

Tartrates are salts of tartaric acid that occur naturally in wine and lead to sediments that cause consumers’ rejection. There are currently different treatments to prevent its occurrence, with cold stabilization being the most traditional and well-known method.

Grape harvest time is one of the most fundamental aspects that affect grape quality and thus wine quality. Many factors influence the decision of harvest; among them technological and phenolic maturity of grape. Technological ripeness is mainly related to sugar concentration, titratable acidity and pH. Conventional methods for chemical analysis of grapes are normally sample-destructive, time-consuming, include laborious sample preparation steps, and generate chemical waste, thereby limiting their utility in online/in-line quality monitoring. Moreover, destructive analyses can be performed only on a limited number of fruit pieces and, thus, their statistical relevance could be limited. This study evaluated the ability of a lab-scale hyperspectral imaging (HYP-IM) technique to predict titratable acidity, organic acid and sugar content of grapes. Samples of Cabernet franc and Chenin blanc grapes were consecutively collected six times at weekly intervals after veraison. The images were recorded thanks to the hyperspectral imaging camera Pica L (Resonon) in a spectral range from 400 to 1000 nm. Statistics were performed using Microsoft Xlstat software. Successively, the berries were analyzed for their sugar (glucose and fructose) and organic acid (malic and tartaric acid) content and titratable acidity according to usual methods.